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United States Patent |
5,253,185
|
Mutchler
,   et al.
|
October 12, 1993
|
Valve diagnostic system including auxiliary transducer box
Abstract
Equipment for acquiring diagnostic data from a valve train parameter that
changes as a result of the operation of a valve (14) in a process plant is
positioned as an auxiliary data acquisition unit (200) in the vicinity of
the valve train. A plurality of sensor lines (P3, P4) are connected
between the auxiliary unit and locations in the valve train where the
parameter changes. The valve is operated so as to generate parameter
signals manifested in a first physical form in the sensor lines. In the
auxiliary unit, the physical form of the parameter signals is converted
into diagnostic signals (E10, E11) having a different physical form. The
diagnostic signals are transmitted to a base data acquisition unit (100)
that is physically distinct from the auxiliary unit.
Inventors:
|
Mutchler; John H. (Wethersfield, CT);
Marriott; William D. (Ellington, CT)
|
Assignee:
|
Combustion Engineering, Inc. (Windsor, CT)
|
Appl. No.:
|
647915 |
Filed:
|
January 30, 1991 |
Current U.S. Class: |
702/183; 137/487.5 |
Intern'l Class: |
G06F 015/20; G08B 021/00 |
Field of Search: |
364/551.01,558,552,509,510
73/168,862.32
137/487.5
|
References Cited
U.S. Patent Documents
4694390 | Sep., 1987 | Lee | 137/487.
|
4816987 | Mar., 1989 | Brooks et al. | 137/487.
|
4855729 | Aug., 1989 | Takguchi et al. | 137/487.
|
4976144 | Dec., 1990 | Fitzgerald | 137/487.
|
5109692 | May., 1992 | Fitzgerald | 137/487.
|
Other References
Soviet Patent Abstracts, PQ General/Mechanical, week 9109 Apr. 17, 1991,
Derwent Publications Ltd.
EP, A1, 0 309 643 (Landis & Gyr) Apr. 5, 1989.
|
Primary Examiner: Harvey; Jack B.
Assistant Examiner: Ramirez; Ellis B.
Attorney, Agent or Firm: L. James Ristas, Mulholland; John H.
Claims
What is claimed is:
1. In a system for acquiring data from valves in process plant flow lines,
wherein each valve has a flow bore, means for sealing the flow bore
against flow, stem means connected to the means for sealing, and a fluidly
driven actuator for selectively moving the stem means between open and
closed positions whereby the means for sealing opens and closes the flow
bore respectively, the system includes a portable data acquition unit
locatable in the vicinity of one of the valves and having a plurality of
electrical input ports for receiving diagnostic signals associated with
said one valve, and wherein the improvement comprises:
an auxiliary unit that is physically distinct from the acquisition unit and
located at another valve, the auxiliary unit having a pressure input port
that is sensitive to variations in fluid pressure, the input port being
fluidly connected at the other valve so as to experience a variation in
fluid pressure during actuation of the other valve, and first output means
connected to the input port of the data acquisition unit, for converting
variations in presssure at the auxiliary unit input port to a commensurate
electrical output signal for delivery as a diagnostic signal to the input
port of the data acquisition unit.
2. The improved system of claim 1, wherein the auxiliary unit input port is
fluidly connected to the actuator of the other valve.
3. The improved system of claim 1, wherein the auxiliary unit input port is
fluidly connected to the flow line associated with the other valve.
4. The improved system of claim 1, wherein the other valve includes a
positioner having a pressure source line and a pressure output line, and
wherein the auxiliary unit input port is fluidly connected to one of the
positioner pressure source or pressure output line.
5. The improved system of claim 1, wherein the auxiliary unit includes an
electrical input port that is sensitive to variations in one of voltage or
current, and second output means connected to an input port of the data
acquisition unit, for converting variations in voltage at the electrical
input port to commensurate variations in output current or converting
variations in current at the electrical input port to commensurate
variations in output voltage, respectively, for delivery as a diagnostic
signal to an input port of the data acquisition unit.
6. The improved system of claim 1, wherein the first output means includes
at least eight electrical output ports.
7. The improved system of claim 5, wherein the first and second output
means include a total of at least eight electrical output ports.
8. In a system for acquiring diagnostic data from a valve train for a
process plant flow line, wherein the valve train includes a flow bore,
means for sealing the flow bore against flow, stem means connected to the
means for sealing, a fluidly driven actuator for selectively moving the
stem means between open and closed positions whereby the means for sealing
opens and closes the flow bore respectively, a valve positioner responsive
to a process control signal, for fluidly energizing the actuator
commensurately with the process control signal, and a valve process
controller remote from the valve, for generating the process control
signal, and the system includes a data acquisition unit having a plurality
of electrical input ports for receiving diagnostic signals from the valve
train, and wherein the improvement comprises:
an auxiliary unit that is physically distinct from the acquisition unit,
the auxiliary unit having a plurality of pressure input ports that are
each sensitive to variations in fluid pressure, at least one of the input
ports being fluidly connected to a point in the valve train that can
experience a variation in fluid pressure during operation of the valve,
and first output means connected to at least one of the input ports of the
data acquisition unit, for converting variations in presssure at the
pressure input ports to commensurate electrical output signals, and
delivering the electrical output signals as first diagnostic input signals
to the input ports of the data acquisition unit.
9. The improved system of claim 8, wherein the auxiliary unit includes a
plurality of electrical input ports that are each sensitive to variations
in one of voltage or current, and second output means connected to at
least one of the input ports of the data acquisition unit, for converting
variations in voltage at the electrical input ports to commensurate
variations in output current and converting variations in current at the
electrical input ports to commensurate variations in output voltage,
respectively, for delivery as second diagnsotic signals to the input ports
of the data acquisition unit.
10. The improved system of claim 8, wherein the first output means includes
at least eight electrical output ports.
11. The improved system of claim 9, wherein the first and second output
means include a total of at least eight electrical output ports.
12. The improved system of claim 8, wherein both the data acquisition unit
and the auxiliary unit are portable in the vicinity of the process plant
flow lines.
13. The improved system of claim 8, wherein at least one of the data
acquisition unit input ports is connected to one valve train and at least
one of the auxiliary unit input ports is connected to another valve train.
14. A method for acquiring diagnostic data from valves in a process plant,
wherein the method comprises the steps of:
positioning a data acquisition unit in the vicinity of one valve;
measuring an operating characteristic of said one valve with the
acquisition unit;
positioning a physically distinct auxiliary unit in the vicinity of another
valve;
sensing in the auxilliary unit, a variable indicative of an operating
characteristic of said other valve;
transforming the sensed variable into a diagnostic signal commensurate with
the variable; and
sending the diagnostic signal from the auxilliary unit to the data
acquisition unit.
15. The method of claim 14, wherein the valves are fluidly actuated and
said variable is fluid pressure.
16. The method of claim 15, wherein the diagnostic signal is an electrical
signal commensurate with the fluid pressure.
17. The method of claim 14, wherein the variable is an electrical voltage
and the diagnostic signal is an electric current commensurate with the
voltage.
18. The method of claim 14, wherein the variable is an electric current and
the diagnostic signal is an electric voltage commensurate with the
current.
19. A method for acquiring diagnostic data from at least one valve train
parameter that changes as a result of the operation of a valve in a
process plant, comprising the steps of:
positioning an auxiliary data acquisition unit in the vicinity of the valve
train;
connecting a plurality of sensor lines between the auxiliary unit and
locations in the valve train where said at least one parameter changes;
operating the valve so as to generate parameter signals manifested in
respective first physical form in the sensor lines;
in the auxiliary unit, converting the first physical forms of the paramater
signals into diagnostic signals having respective different physical
forms; and
transmitting the diagnostic signals to a base data acquisition unit that is
physically distinct from the auxiliary unit.
20. The method of claim 19, wherein the valve is fluidly actuated and the
step of connecting sensor lines includes connecting to at least two
locations where the fluid pressure parameter changes.
21. The method of claim 20, wherein
the parameter signals are manifested in the sensor lines in the physical
form of pressure variations, and
the pressure variations are converted in the auxiliary unit, into
diagnostic signals in the physical form of variations of one of electrical
voltage or current.
22. The method of claim 19, wherein the valve is fluidly actuated in
response to an electrical control signal and
the step of connecting sensor lines includes connecting at least one
pressure line to a location where the fluid pressure changes and
connecting at least one electrical line to a location where said
electrical control signal changes, and
the step of converting includes converting fluid pressure manifested in the
pressure line, into an electrical diagnostic signal.
23. The method of claim 22, wherein said electrical line manifests one of a
voltage or current and the step of converting includes converting the
manifested voltage or current into a current or voltage diagnostic signal,
respectively.
Description
BACKGROUND OF THE INVENTION
The present invention relates to valve diagnostics, and more particularly,
to the diagnosis of valves that are installed in process plant flow lines.
Many types of solenoid and control valves are typically present in process
plants dedicated, for example, to producing electrical power, refining
materials, or producing food. In many such plants, reliable valve
operation not only affects the efficiency of the process or the quality of
the product, but may also have severe safety consequences. Safety
considerations are particularly relevant in nuclear power plants.
Accordingly, it is desirable that some indicator of reliability be
obtainable from measurable characteristics of the valve while installed in
the flow line, i.e., without removing, disassembling, inspecting,
reassembling, and reinstalling the valve. In this context, reliability
refers not only to the availability of the valve to operate when actuated,
but also the effectiveness of the operation, i.e., stroking from a fully
open to a fully closed position when energized within specified limits.
A known approach to such diagnostics includes energizing the valve while
obtaining accurate measurements of, for example, stem thrust or
displacement. By analyzing the relationship of stem thrust, movement, or
similar dependent variable, to the independent energizing variable, such
as electric current, hydraulic pressure, or pneumatic pressure in the
actuator, certain valve behaviors indicative of reliability can be
inferred. Conventionally, such diagnostic techniques rely on the
connection of specially adapted sensors to the individual valve or its
associated components, with the sensor output delivered to a portable data
acquisition unit which is temporarily located in the vicinity of the
valve.
With a growing desire to reduce the time required to obtain data from many
valves in the plant, and to obtain more kinds of data that are useful for
diagnostic purposes, the need has arisen for greater flexibility of the
equipment and methods utilized to acquire diagnostic data.
SUMMARY OF THE INVENTION
It is, accordingly, an object of the present invention to increase the
flexibility for acquiring valve diagnostic data with a dedicated data
acquisitioner unit.
It is a more particular object to augment the capabilities of a data
acquisition base unit situated near one valve, by locating an auxiliary
unit near another valve and transmitting measurements acquired at the
second valve to the base unit at the first valve.
It is yet another object to provide an auxiliary data acquisition unit
whereby data variables in one signal form are converted into electrical
signals by the auxiliary unit, for transmittal to electrical input ports
on a remote base unit.
One embodiment of the invention is used for acquiring data from valves in
process plant flow lines, wherein each valve has a flow bore, means for
sealing the flow bore against flow, stem means connected to the means for
sealing, and a fluidly driven actuator for selectively moving the stem
means between open and closed positions whereby the means for sealing
opens and closes the flow bore respectively. A portable data acquisition
unit is locatable in the vicinity of one of the valves, and has a
plurality of electrical input ports for receiving diagnostic signals
associated with the one valve. An auxiliary unit that is physically
distinct from the acquisition unit, is located at another valve. The
auxiliary unit has a pressure input port that is sensitive to variations
in fluid pressure. The input port is fluidly connected at the other valve
so as to experience a variation in fluid pressure during actuation of the
other valve, and has first output means connected to the input port of the
data acquisition unit, for converting variations in presssure at the
auxiliary unit input port to a commensurate electrical output signal for
delivery as a diagnostic signal to the input port of the data acquisition
unit. Preferably, the auxiliary unit also includes means for converting
one type of electrical signal, such as voltage or current, into another
type of electrical signal, such as current or voltage, respectively.
Alternatively, the auxiliary unit can be used in conjunction with a base
unit to obtain a wider variety of data from a single valve or associated
valve train.
A general method for acquiring diagnostic data from valves in a process
plant according to the invention, includes the steps of positioning a data
acquisition unit in the vicinity of one valve and measuring an operating
characteristic of the one valve with the acquisition unit. A physically
distinct auxiliary unit is positioned in the vicinity of another valve. In
the auxiliary unit, a variable indicative of an operating characteristic
of the other valve is sensed and transformed into a diagnostic signal
commensurate with the variable. The diagnostic signal is then sent from
the auxilliary unit to the data acquisition unit.
With the auxiliary unit used in conjunction with a basic data acquisition
unit of the type described below, a relatively large number of electrical
signals (current or voltage) in a pneumatic or hydraulic control loop of
the valve, can be monitored. This includes but is not limited to signals
associated with E/P or I/P positioners, solenoids, limit switches,
position indicators and controllers. Additionally, the user may
temporarily install and monitor a variety of instruments to assist in
monitoring valve performance. These include strain gauges, load cells,
accelerometers, and thermocouples. Although the base test unit preferably
includes a sufficient number of electrical input ports and appropriate
recording channels to permit the user to obtain significantly more data
than had previously been acquired for valve diagnosis in the field, this
capability is augmented by the auxiliary unit, which has the capability to
monitor additional pneumatic and hydraulic pressures remote from the base
unit.
The auxiliary unit includes several pressure transducers which tie into the
base unit. By using one or more auxiliary units, multiple pressure signals
(pneumatic or hydraulic) can be monitored from, and recorded in, the base
unit. This allows the user to monitor up to, for example, twelve pressure
channels for one valve, or to simultaneous monitor fewer pressure channels
but from more than one valve. The auxiliary unit can be tied in closer to
the pressure source to reduce pressure lag, relative to a direct
connection to the base unit. The auxiliary unit also allows for conversion
of current signals into voltage signals for delivery to voltage sensitive
ports in the base unit, or vice versa.
In general, the auxiliary unit according to the invention receives sensed
valve parameter signals in one form remote from a base data acquisition
unit, and converts the signals into another form that is transmitted to
the base unit. Preferably, pressure signals are converted to electrical
voltage or current signals.
BRIEF DESCRIPTION OF THE DRAWING
These and other objects and advantages of the invention will be described
below in the context of the preferred embodiment, with reference to the
accompanying drawing, in which FIG. 1 is a schematic of the auxiliary unit
of the invention, as part of a more comprehensive valve diagnostic system.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 is a schematic representation of the invention installed at part of
a system 10 for acquiring data from valves 12,14. For convenience,
structures found on both valves have been given the same muneric
identifier, except that those associated with valve 12 will have the
suffix "a" and those associated with valve 14, "b". When similar
structures on both valves are referenced, the suffix will not be used.
These valves may be of substantially any type, and in any event would
include a valve body 16a,16b which has a flow bore (not shown) in fluid
communication with the respective process flow line 18. It will be
understood that each valve has means within the body for sealing the flow
bore against flow. A stem, shaft, or similar transmission element 22
(hereinafter generally referred to as "stem") is moved by the valve
actuator 20, whereby the stem 22 positions the sealing member within the
valve body between open and closed flow conditions.
Although usable for testing other types of valves, the present invention
will be described in the context of fluidly operated valves, whereby the
actuator is energized by pneumatic or hydraulic pressure. Typically, each
valve train includes an associated positioner 24 which has an output line
26 through which fluid pressure is delivered at a controlled rate to the
respective actuator 20. The positioner inputs would, in the case of a
pneumatic valve, include a source of compressed air 28, and a source of
electric power 30. Both the initiation and time dependency of the pressure
supplied by the positioner 24 to the actuator 20, is specified by a valve
controller 34 via an electrical line 32. The controller is typically
remote from the positioner 24, e.g., the controller 34 is in the plant
central control room, whereas the positioner 24 is on or at the valve.
Typically, for control valves, the positioner 24 receives as an input, a
signal from line 25, commensurate with the position of the stem 22. The
position data from input 25 are compared with the demand or desired
position from signal 32, according to conventional logic within positioner
24, whereby the appropriate pressure is delivered to actuator on line 26.
A diagnostic or test base unit 100 is connectable to at least one valve 12,
and associated valve train, preferably with the capability of superseding
or overriding the controller 34 and/or positioner 24, whereby the valve
can be actuated according to a predetermined, time-dependent program. The
base unit 100 has a first input port 102 connectable to a source 104 of
fluid pressure, e.g., compressed air. This source may either be
transported to the vicinity of the valve along with the base unit 100, or,
in a more typical situation, source line 104 is connected to air pressure
lines that are available throughout the process plant. Similarly, a second
input port 106 is connectable to a source of electrical power 108, such as
an electrical outlet in the plant.
The base unit 100 has a first output port 110 that is fluidly connected
within the unit to port 102, for delivering a controlled fluid pressure
from the unit along line 112. Line 112 is selectively connectable to line
26, i.e., directly to actuator 20, downstream of positioner 24a. A second
output port 114 is electrically connected within the base unit to the
second input port 106, for delivering a controlled electrical signal from
the unit on electric line 116. The control signal on line 116 emulates the
control signal normally provided by controller 34 along line 32a. When
line 116 is input to positioner 24a, via line 32a or otherwise, the valve
12 can be controlled through its positioner 24a, independently of the
controller 34.
It should be appreciated that it is well within the skill of the ordinary
practitioner in this field to transform a supply of compressed air at a
given pressure in line 104, into a time-dependent pressure variation in
line 112, and, similarly, to transform a source of electrical power at 110
volts A.C., into a time-dependent D.C. voltage signal along line 116.
Thus, the unit 100 includes test program means for converting the fluid
pressure at the first input port 102 into a controlled, time-dependent
fluid pressure at the first output port 110, and for converting electrical
power at the second input port 106 into a controlled, time-dependent
electrical signal at the second output port 114.
The test program means can include conventional transformer hardware with
dials or the like, whereby the operator can vary the outputs at ports
110,114 manually. In a more desirable implementation, particular,
predetermined, time-dependent output pressures and voltages at ports
110,114 are specified by several different converter or transformer paths
within the unit, with switches whereby the operator can select one of the
plurality of "hard wired" pressure and electrical test programs. In the
preferred embodiment, a computer 118, which may be integral with or
separate from the base unit 100, specifies the test programs. As used
herein, the term "computer" is intended to mean a programmable
microprocessor, with or without associated peripherals such as a digital
mass storage device, keyboard and display, or equivalent interfaces. The
important aspect of the computer 118 is that a time-dependent fluid
pressure, and a time-dependent electrical signal, are independently
specified and output from the unit 100 as a result of test programs that
are stored in, and executed by, the digital processing means associated
with the unit.
The portable base unit 100 and associated digital processor 118 ar
positioned in the vicinity of a valve 12 to be tested. Actuator 20a, for
operating the valve, can be energized in the most straightforward manner
by connecting pneumatic line 112 from port 110 directly to the actuator
20, typically through a T fitting in line 26a. The positioner 24a is then
overridden or otherwise deactivated by any of a variety of available
techniques such as shutting off air and electrical sources 28a,30a, or
sending an appropriate signal along line 32a from the controller 34. In
this mode of operation, the actuator 20a is energized solely and directly
by the pressure in line 112, which has a time-dependence specified
independently of the controller 34, by the test program stored or
otherwise defined by the unit 100.
A significant advantage of energizing the actuator 20a via the test program
and line 112, is that a time-dependent energizing that would not
ordinarily be useful for flow control purposes, but which would be
revealing of information useful for diagnostic purposes, can be achieved
with the present invention, without modification of the normal control
algorithm in controller 34. Moreover, with the computer-implemented
embodiment, the operator can select either a known, stored program for
execution of the pressure control on line 112, or the operator can modify
(and reproduce) the pressure amplitude, or time dependency during the
course of performing a sequence of valve energizing cycles. The
information flow along line 119 can flow between a base unit and distinct
computer 118 as shown in FIG. 1, or the flow can be entirely within the
base unit if the computer is incorporated therein.
The unit 100 is used in conjunction with a direct measurement of the
actuator pressure Pl at 122, and the direct measurement of stem movement
as manifested by a sensor voltage El at 120. Preferably, the base unit 100
includes a measurement input section 124 having a plurality of pressure
input ports such as 126,128. Line 122 is directly attached to actuator
20a, and directly connected to measurement port 126. Pressure transducers
internal to the base unit 100 convert pressure variations into measured
values which are recorded, preferably on magnetic memory or the like
associated with computer 118.
Base unit 100 also preferably includes an electrical measurement input
section 130 including a plurality of electrical input ports 132, for
receiving electrical signals of interest to the diagnostic analysis. One
such signal is E1, the voltage output from an LVDT or other intrusive or
not intrusive sensor that is responsive to the movement or thrust of stem
22a or similar member in the thrust transmission between the actuator 20a
and the valve member in body 16a. It should be appreciated that other
pressure and/or electrical signals indicative of valve operation or
condition, such as the pressure in positioner air supply line 28a,
represented at P2, can be input to the base unit at, for example, port
128.
The base unit 100 has been described above, in terms of its unique
capability to override the controller 34 so as to energize the valve 12
according to a desired or known time dependency. The unit output can be
pneumatic when it is desired that the positioner be bypassed, or
electrical when it is desired that the operation of the positioner be
included within the diagnosis.
As shown in FIG. 1, the base unit 100 is preferably used in conjunction
with an auxiliary unit 200 in accordance with the present invention,
whereby a variety of additional measurement data can be acquired for a
single valve 12, or a plurality of valves 12,14. It should be appreciated
that the auxiliary unit 200 can be used with a base unit that, unlike the
unit 100 described above, does not have the program controlled outputs
from ports 110,114. Moreover, the base unit is not required to be portable
or locatable in the vicinity of a valve, although it is preferred that
both units 100 and 200 be portable.
With reference now to a general auxiliary unit 200, there are shown a
plurality of electrical inputs E2-E5. Signal E2 is delivered to the
auxiliary unit as a measurement of the electrical control signal from
controller 34 as delivered along line 32a to positioner 24a. The
controller 34 would normally be remote from valve 12, and therefore
temporarily installing a direct electrical line from the controller to the
base unit 100, which is at valve 12, would not be convenient. The
auxiliary unit 200 can be near controller 34, remote from both the base
unit 100 and the valve 12 to be tested, thereby affording the flexibility
to receive a voltage signal E2 in the auxiliary unit and to amplify or
otherwise condition the signal E2 for delivery from an electrical output
port 206, as electrical signal E6 to section 130 of the base unit. Signal
E4 on line 32b can also be handled in this fashion for auxiliary unit
output E8.
Similarly, auxiliary unit 200 can be located in the vicinity of valve 14,
to receive the electrical signal E3 from the stem displacement sensor,
into a port 202 for delivery through port 206 and line E7 to base unit
section 130.
In another variation, the current supplied by a source of electrical power,
for example at line 30b, may be readily sensed, but the input at a port
132 of the base unit may be adapted to receive a voltage rather than a
current signal. The auxiliary unit 200 can in this instance receive a
current signal E5 through an input port 202, and deliver a commensurate
voltage signal through an output port E9.
The auxiliary unit 200 also has a plurality of pressure input ports 204
which receive varying fluid pressures through lines P3, P4, P5 and P6,
each of which is converted by a transducer into a commensurate electrical
output signal E10, Ell, E12 and E13, for delivery to section 130 of base
unit 100. Although the base unit 100 may have pressure input ports 126,128
in section 124 for connection to a nearby valve such as 12, the receipt of
direct pressure variations from a more remote valve such as 14, would
degrade the measurement. Accordingly, with the auxiliary unit 200 situated
near the other valve 14, pressure measurements such as P3 from actuator
20b can be delivered to the auxiliary unit 200 and converted to an
electrical signal for delivery over a longer distance without degradation,
to the base unit 100.
It should be appreciated that the axuiliary unit 200 can have any desired
number of electrical and pneumatic input ports 202 and 204, and a
corresponding number of electrical output ports 206. As an example, at
least eight, and preferably twelve ports 206, and a corresponding number
of electrical input ports 132 on base unit 100, has been found desirable.
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